U.S. Pat. No. 4,961,074 to Martinson discloses radar detectors, which are capable of monitoring at least two frequency bands. A broadband antenna is provided, together with a mixer comprising an anti-parallel pair of diodes, and at least one local oscillator. The local oscillator frequency is mixed with radar frequency from the antenna to produce an intermediate signal which is amplified, further down converted, detected and fed to signal processing circuitry to actuate an alarm when radar frequency of interest is detected. The disclosed detector uses one mixer in the first stage to cover all bands, comprises no pre-amplifiers and no synthesized LOs.
U.S. Pat. No. 4,952,936 to Martinson discloses radar detection devices sensitive to signals from various different frequency bands. A broadband antenna is provided, together with a mixer and a plurality of local oscillators. Signals from the local oscillators are mixed one at a time with signals from the antenna, there being one local oscillator signal for each radar frequency or pair of frequencies of interest, which may be received by the antenna. Each local oscillator signal is chosen so that when it is mixed with the respective radar frequency signal, an intermediate signal is produced, which is the same for all mixtures. This intermediate signal is further down converted and fed to signal processing circuitry to produce an alarm when radar frequencies of interest are detected. The disclosed detector uses the same antenna, pre-amplifier and mixer to cover all bands.
U.S. Pat. No. 4,630,054 to Martinson discloses radar detection and signal processing circuits. Following a front end having an RF and local oscillator mixer to an I.F., the signal is then further mixed against a signal from a swept frequency oscillator, in the presence of a microwave frequency signal. The output of a band pass filter goes to a detector for frequency modulated intermediate frequency signals, and that detector has at least a first output signal that is fed to two pairs of complementary paired comparators, the outputs of which are set to low and high threshold levels. The sensitivity of the circuit may adjust up or down according to the number of low threshold signals that are detected; or dynamically if too many low threshold signals are detected in a small group of time cells. The disclosed detector detects and stores signals only at the amplitude level. An alert for out-of-band signals is given if they exist for a predetermined time. No pre-amplifier is used at the front-end.
U.S. Pat. Nos. 4,750,215 and 4,862,175 to Biggs et al disclose a radar-warning receiver having a police radar signal detection circuit which generates evaluation signals, the state of which indicates the voltage level relative a threshold voltage of a discriminator output, as the local oscillator is swept through the radar band. The times during which the evaluation signals are in one state or the other are utilized to identify whether the received signal is from a fixed frequency source or a variable frequency source. The disclosed detector detects signals only at the amplitude level. No pre-amplifier is used at the front-end.
U.S. Pat. Nos. 4,954,828 and 5,079,553 to Orr disclose a police radar warning receiver including a DSP circuit having a correlator and a peak detector to provide after each sweep of a swept local oscillator a dynamic threshold for that sweep as affected by all prior sweeps and against which information from that sweep is evaluated to determine whether to generate an alarm enable indicative of receipt of a police radar signal. The disclosed detector detects signals only at the amplitude level.
U.S. Pat. Nos. 5,300,932 and 5,250,951 to Valentine, et al. disclose a police radar signal detector which detects and monitors radar signals from up to nine radar sources until a detected radar signal has not been redetected for a given number of detector operations, or spectrum sweeps, or until a detected signal has been displaced by a higher priority radar signal. In the police radar signal detector disclosed, a user of the detector is advised not only of the presence of detected radar signals, the frequency band of detected radar signals and the relative field strength of the signals but also of the number of different radar signal sources which are transmitting signals toward the user's motor vehicle. In addition, the directions of radar sources are determined. The determination of which antenna has received the signal is based on detecting difference of amplitude between back and front antennae. The disclosed detector detects signals only at the amplitude level.
U.S. Pat. No. 5,305,007 to Orr et al. discloses a wideband radar detection apparatus including a signal detection section, a high rate signal processing section and a low rate signal processing section. The signal detection section sweeps through a range of pre-selected frequencies and generates an output signal having a pair of single cycle sinusoids for every detected signal. The output signal is provided to the high rate signal processing section and a Sliding Window DFT is performed thereon to generate a set of complex values that are related to the fundamental energy content at consecutive points in the sweep. The low rate signal processing section controls sweep parameters and also evaluates the complex values. If the magnitude of the complex values exceeds a predefined threshold, then an alert is indicated. The disclosed detector detects only the magnitude of the detected signals, has no pre-amplifiers and no synthesized LOs.
U.S. Pat. No. 6,175,324 to Valentine, et al. discloses a frequency scheme for a police radar detector, which enables sweeping of the X, K, Ku and Ka radar bands. The frequency scheme requires two initial frequency conversions for detection of the X, K and Ka radar bands and a single initial frequency conversion for the Ku radar band with single initial frequency conversion being enabled by disabling the second mixer. During sweeping of the X, K and Ka bands, selectable sideband suppression is employed to reduce undesired image sidebands and noise prior to the second frequency conversion. In addition, noise at the second IF frequency is reduced to prevent this noise from feeding through the second mixer into the second IF amplifier. During the Ku band sweep, the second mixer is bypassed and shunting of signals at the second IF frequency is disabled so that these signals enter the second IF amplifier. The disclosed detector uses a single wideband stage for all bands.
U.S. Pat. No. 5,900,832 to Valentine, et al. discloses an input stage for a police radar detector including a single mixer together with at least one preamplifier to detect radar signals in the X, K and Ka bands. Some or all of the receiver responses are swept independently with the preamplifier or preamplifiers being enabled one at a time as appropriate for each band being scanned. The Ka band signals are coupled to a single mixer through a preamplifier, which permits multiple responses to be swept in the Ka band, or passively, to receive dual responses in the Ka band. The disclosed detector uses multiple pre-amplifiers for one mixer, thus being able to sweep only one band at a time.
U.S. Pat. No. 5,068,663 to Valentine, et al. discloses a radar detector for use in a motor vehicle employing amplitude detection. Amplitude signals are generated by down-converting received signals using a series of mixers, one of which is swept to insure signal detection, and compared to a threshold which is controlled such that noise is detected by the comparison on average a selected period of time. After passing a first test of persistence, the signals are verified by means of frequency modulating the first of the series of mixers, detecting the frequency modulation and correlating the detected frequency modulation to determine whether the signal is valid and if so, to which radar frequency band the signal belongs. The disclosed detector provides only amplitude detection of a signal. Out-of-band signals may be detected, if they exist for a sufficient time, due to wideband detection.
Due to the high density of communication signals, satellite, radar systems etc., that cause high false alarm rate when using wideband detectors, there is need for a signal detection device with higher sensitivity, to enable improved in-band signal detection, while suppressing out of band signals.